Ok, I fixed the initial error by editing
/usr/share/perl5/EBox/UsersAndGroups.pm and set
MAXGROUPLENGTH to be 40. However, now it is giving another one:
2010/02/11 14:45:12 DEBUG> ebox-ad-sync:296 main::getPrincipalName - [ad-sync] can't get userPrincipalName for...
And it says that about a number of users. Still now change otherwise, I still am only getting the same few users imported as before. Not sure what would be causing this. Thoughts?